Rare causes of respiratory insufficiency in newborns.

Congenital lung masses (CLM) the rare group of causes of acute respiratory insufficiency (RI) in newborns include congenital airway pulmonary malformation (CAPM), congenital overinflation, bronchopulmonary sequestration, and bronchial atresia. The presenting group consists of 13 newborns who were admitted to the Neonatal Department of Intensive Medicine (NDIM) during January 1st 2015-December 31st 2019 (8 males, 5 females, 2 premature/11 term newborns, spontaneous delivery: 2, caesarean section: 11) with positive prenatal diagnosis of CAPM in all cases. In 2 cases prenatal intervention was performed (drainage of the amniotic fluid, attempt of thoracentesis). Signs of acute RI immediately after delivery were seen in 5 newborns. Postnatal echocardiographic investigation confirmed the presence of increased pulmonary pressure in 8 patients, no patient had congenital heart abnormality. A thorax x-ray was positive also in asymptomatic patients. Computed tomography in patients brought detailed information about the position, size and character of CAPM. Six patients underwent surgery. In 15.4 % right lungs were affected by cystic malformation and in 23 % left lungs were affected. A final diagnosis of CAPM was confirmed in 5 patients using histopathologic examination. Multidisciplinary cooperation during prenatal as well as postnatal period is necessary.

On infusion of high-dose ascorbate in treating cancer: Is it time for N-acetylcysteine pretreatment to enhance susceptibility and to lower side effects?

Ascorbate administered intravenously gives a high plasma concentration of this drug. Clinical trials with pancreatic carcinoma patients revealed their prolonged survival if treated with intravenous ascorbate. On the other hand, high plasma ascorbate concentration leads to severe side effects, such as nephrotoxicity. In the present paper, we advocate to lower intravenous ascorbate dosage along with monothiol N-acetylcysteine pretreatment due to anticipation of the same therapeutic effect but less or none of side effects. We describe in detail molecular mechanism of ascorbate action to be potentiated by N-acetylcysteine, as observed under in vitro conditions. Providing further arguments, we believe that the same mechanism may be employed in vivo.

Meet interesting abbreviations in clinical mass spectrometry: from compound classification by REIMS to multimodal and mass spectrometry imaging (MSI).

This feature article discusses two modern mass spectrometry abbreviations in their clinical applications. Rapid evaporative ionization mass spectrometry (REIMS) is reported as a molecular classification tool useful for spectral features definition prior to mass spectrometry imaging (MSI). REIMS is appreciated not only as an ionization technique coupled with a surgical device but particularly as a biomarker discovery tool. For more complex understanding of pathological processes at cellular and molecular levels, the importance of multimodal approach in imaging applications is documented in the context of fiducial markers needed for hyperspectral data fusion collected by optical microscopy, elemental and molecular MSI. Finally, pathogen inactivation needed prior to the sectioning of the infected tissue is reported, and the impact of formaldehyde crosslinking to signal reduction is discussed.

Hyaluronan peroxidation is required for normal synovial function: an hypothesis.

Despite widespread use of antioxidants, reactive oxygen species have important functions in normal tissues. Herein, we present an example of a physiological role for free radicals, and in particular, reactive oxygen species, that are suppressed by anti-oxidants. Free radicals catalyze the degradation of hyaluronan in synovial fluid, a tissue in which hyaluronidase activity is barely detectable. Articular cartilage requires a low oxygen environment. The process of hyaluronan peroxidation consumes significant amounts of molecular oxygen, thus keeping the tension of oxygen in the joint at a low but physiologically critical level. One concern is the change in physical activity between day and night, with periods of joint hyperemia and ischemia, respectively. Increased oxygen and the resulting oxidative stress would lead to chondrocyte dysfunction and cartilage damage. A mechanism for keeping oxygen levels low is required. We postulate that a mechanism indeed exists for the removal of excess oxygen. High-molar-mass hyaluronan turnover in synovial fluid utilizes peroxidative degradation, during which oxygen is massively consumed. The peroxidation itself may be initiated by hydrogen peroxide, which is produced by chondrocyte mitochondria, that can diffuse into the synovial fluid. The resulting decrease in available oxygen down-regulates hyaluronan peroxidation. This in turn prevents excessive oxygen consumption. It appears that free radicals and reactive oxygen species may be components of normal physiology, particularly in the synovial fluid of joints and articular cartilage. It is suggested therefore that indiscriminate use of anti-oxidants, vigorously promoted currently by health professionals and the health industry, be approached with caution.

Antioxidants in treating pathologies involving oxidative damage: an update on medicinal chemistry and biological activity of stobadine and related pyridoindoles.

Pathologies involving oxidative stress are indicative of malfunction of endogenous antioxidant capacity. Numerous efforts were made to design and synthesize biologically active antioxidants and free oxygen radical scavenging substances that could improve the endogenous antioxidant status. The antioxidant and reactive-oxygen-species-scavenging activity of STB was well demonstrated in many in vitro and in vivo studies. These properties of STB seem to be closely related to its beneficial effects in models of oxidative-stress-involving pathologies, including myocardial infarction, stroke, neurodegenerative disorders, hypoxic-ischemic tissue injury, diabetic complications, chronic inflammation, etc. STB has a good affinity to lipids and exerts its protective activity against free-radical-mediated damage by preventing lipid peroxidation. Rather than interacting with the radicals initiating lipid peroxidation, STB was shown to act in its propagation stage via scavenging peroxyl and/or alkoxyl radicals. STB was also found to protect proteins, predominantly by a mechanism involving protection of thiol groups and by preventing oxidation of amino acids. The first findings on antioxidant and pharmacodynamic effects of STB, tested in a variety of biological models, were summarized in 1998. Recently, chemical modification of STB, which we considered as the leading structure, led to the synthesis of pyridoindole derivatives with significantly increased intrinsic antiradical activity and overall antioxidant efficacy compared to the parental molecule. The present paper provides a complete overview of the literature published since 1998 on both STB and STB congeners. Moreover, appropriate structural modifications of STB provided the opportunity to modulate lipophilicity and acidobasic behavior, thus optimizing bioavailability of the novel derivatives and attenuating their unwanted sideeffects, with the result of decreased toxicity. Hence, STB congeners might be prospectively used as medicinal antioxidants, i.e. remedies effective in conditions involving oxidative stress-mediated injury.

Controversy of free radical hypothesis: reactive oxygen species--cause or consequence of tissue injury?

For a decade or two, the hypothesis of causality of various disorders by reactive oxygen species (ROS), due to their potentially harmful effect towards cellular constituents, is one of the most frequently cited in biomedical sciences. In fact, the ROS-mediated alterations of biomacromolecules are considered to be essential events in the etiopathogenesis of those diseases where involvement of ROS has been indicated. ROS easily react in vitro with most biological molecules, causing their degradation and destruction. This may implicitly suggest that, when excessively produced in vivo, ROS are deleterious to integral components of the cell and cause their dysfunctions. Some experimental data indicate that ROS-mediated lipid peroxidation, protein oxidation and oxidative alterations to nucleic acids are crucial events of unfavorable actions of ROS. Yet the most convincing evidence, i.e. unambiguous inhibition of tissue injury by pretreatment with antioxidants, has not been provided. On the contrary, there are quite a few papers reporting failure in applying antioxidants to heal those pathologies where the causal role of ROS was supposed. Other papers reported serious complications arising from antioxidant therapy, which is quite in contradiction to its expected effect. On the other hand, an increasing number of recent findings have provided evidence of a key role of ROS in both intracellular signaling and intercellular communication, processes involved in maintaining homeostasis. Hence, some investigators consider excessive production of ROS to be rather a "smoke after the fire" than "a deleterious fire" itself, suggesting the occurrence of overproduced ROS as being the consequence of some primary damage. The present paper aims at summarizing some pros and cons of various opinions with an attempt to help better understand the involvement of ROS in tissue injury.

On augmentation of adenosine-mediated negative dromotropic effect by K+ released during myocardial ischemia.

The present study was designed to investigate mechanisms of adenosine (ADO)-mediated prolongation of conductivity through the atrioventricular (AV) node during myocardial ischemia. Using the Langendorff preparation of the guinea pig heart, we tested the hypothesis that extracellular potassium concentration elevated due to ischemia could augment ADO effect. Exposure of the heart preparation to either stop-flow or hypoxic Krebs-Henseleit solution (KH) inhibited AV node conductivity observed as an increase in SH interval, and finally resulted in AV block. Superficial potassium concentration ([K+]s), recorded simultaneously increased in response to each stop-flow or hypoxia. Application of 0.1 mM BaCl2 markedly increased the SH interval, yet it did neither protect the heart from hypoxia-evoked AV block nor did it prevent hypoxia-induced [K+]s elevation. Neither did perfusion of the myocardium with modified KH containing 8 mM K+ affect the hypoxic AV block and [K+]s increase. The hypoxic effects were not affected by adenosine A1 agonist N6-cyclopentyl-adenosine (CPA, 30 nM). In the presence of CPA, application of high-K+ KH, where potassium was elevated to the value of hypoxic level, did not affect the SH interval. On the other hand, adenosine deaminase (ADA, 4 U/ml) significantly attenuated the hypoxic AV block. This indicated an involvement of endogenous ADO. Yet, in the presence of both ADA and CPA, the application of the high-K+ KH did not affect the SH interval. We concluded that increased extracellular [K+], elevated due to hypoxia, did not participate in the hypoxia-induced AV block mediated by ADO.

Effect of melatonin and stobadine on maternal and embryofoetal toxicity in rats due to intrauterine hypoxia induced by phenytoin administration.

The aim of the present study was to test the hypothesis that the natural antioxidant melatonin (MEL) and the synthetic antioxidant stobadine (STO) could reduce the incidence of maternal and embryofoetal toxicity in rats due to intrauterine hypoxia. Chronic hypoxia was induced pharmacologically by the administration of the anticonvulsant phenytoin (PHT) during the entire period of pregnancy. PHT disturbed the normal course of pregnancy, affected reproductive parameters and increased the incidence of skeletal anomalies. MEL did not protect the PHT-induced development toxicity in rat. On the other hand, STO partially prevented PHT-induced reduction of foetal and placental weights. Administration of STO also decreased the frequency of pre- and post-implantation loss and resorptions in the PHT group. We concluded that pretreatment of pregnant rats with STO prevented to a certain extent reproductive and foetal development alterations caused by chronic intrauterine hypoxia.

The effects of H2O2 on electromechanical activity of the ileum longitudinal muscle.

The effects of H2O2 on electrical and mechanical activity of the longitudinal layer from the guinea-pig ileum were studied using sucrose-gap technique and the influence of H2O2 on ionic current was investigated in single smooth muscle cells by the patch-clamp method. In most of the preparations tested, the spontaneous activity observed was composed of slow waves with superimposed action potentials (APs). Both were resistant to tetrodotoxin and atropine. H2O2 (1 mmol/l) evoked sustained 3-5 mV membrane depolarisation, doubled the amplitude of the slow waves and increased their frequency, augmented the APs and reduced their splitting. These changes were accompanied with significant contraction, which had an amplitude comparable to that of the tonic component of 50 mmol/l K+-induced contraction. Calcium-free solution caused membrane depolarisation, reduction of the slow wave amplitude and frequency, disappearance of APs and decreased the mechanical tension of the preparations. Application of H2O2 (1 mmol/l) into the zero-calcium bath solution recovered the APs, which was accompanied by a low amplitude contraction. H2O2 (up to 1 mmol/l) increased the L-type calcium current (I(Ca)) both under conventional whole-cell patch-clamp configuration and under amphotericin-perforated patches by 16 +/- 3%. These data demonstrated that contractile response of the ileum longitudinal smooth muscle preparation evoked by H2O2 was mainly due to the enhanced electrical activity.

Hinokitiol, a selective inhibitor of the platelet-type isozyme of arachidonate 12-lipoxygenase.

Hinokitiol (4-isopropyltropolone), a constituent of Japanese cypress, reversibly inhibited platelet-type 12-lipoxygenase with an IC(50) of 0.1 microM, and the enzyme activity was almost lost at 1 microM. The compound was much less active with other lipoxygenase enzymes with higher IC(50) values (leukocyte-type 12-lipoxygenase, 50 microM; soybean lipoxygenase, 17 microM; 15-lipoxygenase-1, >100 microM; 5-lipoxygenase, 17 microM). Hinokitiol up to 100 microM had almost no effect on cyclooxygenases-1 and -2. Their structure-activity relationship examined with various tropolone derivatives indicated the requirements of the 2-hydroxyl group and 4-alkyl group for the potent and selective inhibition of platelet-type 12-lipoxygenase.

Effect of stobadine on lipid peroxidation in brain and heart after ischemia and reperfusion of the brain.

Stobadine (ST), a novel drug with pyridoindol structure, was recently found to prevent reperfusion injury in rat brain. The aim of the present study was to reveal whether ST may prevent peroxidative changes in the heart and brain that were triggered by postischemic reperfusion of the brain. In the brain, reperfusion significantly increased the contents of malondialdehyde (MDA) by 43.8% and conjugated diens (CD) by 24.5% when compared with the end of ischemia. In the heart, contents of MDA and CD in reperfusion became elevated three fold and by 41.7%, respectively, when comparing to the values at the end of ischemia. In the heart, no significant changes in activities of the superoxide dismutase (SOD) and glutathione peroxidase (GPx) induced by ischemia or reperfusion were detected. In contrast, reperfusion induced a slight decrease in GPx activity in the brain. In accordance with our previous results, an application of ST (2 mg/kg) to the femoral artery shortly prior to reperfusion of the ischemic brain, prevented significantly MDA and CD accumulation in brain. Nevertheless, ST was not able to prevent the brain-ischemia/reperfusion-induced elevation of MDA and CD contents in the heart.

Affinities of various mammalian arachidonate lipoxygenases and cyclooxygenases for molecular oxygen as substrate.

In an attempt to study affinities for molecular oxygen of mammalian arachidonate oxygenases, which remain unclarified at present, we determined activities of platelet-type 12-lipoxygenase, leukocyte-type 12-lipoxygenase, 5-lipoxygenase, 15-lipoxygenase, cyclooxygenase-1 and cyclooxygenase-2 at various oxygen concentrations. Activities of all the tested enzymes were assessed by oxygenation of radioactive arachidonic acid under hypoxic conditions, and part of the enzymes were also assayed by monitoring oxygen consumption. Their Km values for oxygen ranged between 10 and 26 microM. These results should be considered in investigations of arachidonic acid metabolism in pathophysiological processes associated with hypoxia.

Hypoxia-induced inhibition of calcium channels in guinea-pig taenia caeci smooth muscle cells.

1. The effects of hypoxia on whole-cell current in single smooth muscle cells and on a high K(+)-induced contraction of strips of the guinea-pig taenia caeci were studied. 2. In physiological salt solution (PSS) and K(+)-based pipette solution, hypoxia (PO2 = 20 mmHg) reversibly inhibited both the inward Ca2+ current (ICa) and outward Ca(2+)-activated K+ current (IK(Ca)) components of the whole-cell current. 3. In PSS and Cs(+)-based pipette solution, hypoxia reversibly suppressed ICa by 30 +/- 5% at 0 mV. 4. When Ba2+ was used as a charge carrier, the IBa was suppressed by hypoxia in a potential-dependent manner, with the maximum of 40 +/- 7% at +10 mV. Alterations of concentrations of EGTA, GDB beta S or ATP in the pipette solution did not change the inhibitory effects of hypoxia on ICa and IBa. 5. In PSS with 2 mM CaCl2 replaced by CoCl2, hypoxia did not affect the Ca2+ influx-independent potassium current. 6. In cells voltage clamped at -20 mV hypoxia reversibly inhibited the spontaneous transient outward currents. 7. The response of high K(+)-contracted taenia caeci to hypoxia was composed of an initial rapid relaxation followed by a small transient contraction and slow relaxation. The transient contraction was blocked by atropine (1-10 microM), while relaxations were unaffected by atropine and guanethidine (10 microM). 8. The results show that hypoxia reversibly inhibits ICa and secondarily suppresses IK(Ca) due to decreased Ca2+ influx through Ca2+ channels. 9. It is suggested that inhibition of ICa was responsible for the rapid relaxation, whereas transient contraction may have been due to release of acetylcholine from nerve terminals upon hypoxia.

Afferent C-fibres release substance P and glutamate.

Capsaicin is currently used as a specific pharmacological tool for investigation of functions of primary afferent C-fibres. Their peripheral terminals play an important role in "neurogenic inflammation," mediated by released substance P and calcitonin gene related peptide, whereas in the mediation of central functions, activation of the N-methyl-D-aspartate (NMDA) receptors has recently been demonstrated. A method for continuous monitoring of glutamate concentration was used to study mechanisms of capsaicin-induced glutamate release from rat spinal cord slices. Both capsaicin and substance P released glutamate from spinal dorsal horns in a concentration-dependent manner (EC50 = 0.53 +/- 0.07 and 0.37 +/- 0.06 microM, respectively). The NMDA antagonist MK-801 (10 microM) had no effect on evoked glutamate release, whereas the tachykinin (NK-1) antagonist CP-99994 (10 microM) reduced responses to both stimuli (p < 0.001). In capsaicin-desensitized rats, evoked glutamate release from dorsal horns was significantly decreased yet not completely abolished. Although the evoked glutamate release from ventral horns was markedly smaller than that from dorsal horns, the normalized responses to capsaicin and to substance P were similar. This might be explained by smaller amounts of mobilizable glutamate in ventral horns. Our findings confirmed the ability of capsaicin to release glutamate mainly from the afferent C-fibres in the spinal cord. The observed effect of exogenous substance P and inhibitory action of the NK-1 antagonist indicate facilitation of capsaicin-induced glutamate release by coreleased substance P.

Evidence for the participation of glutamate in reflexes involving afferent, substance P-containing nerve fibres in the rat.

1. Responses mediated, either peripherally or centrally, by substance P-containing primary afferent C-fibres were investigated in the rat following impairment of axonal transport by colchicine (120 micrograms kg-1, i.p., daily for 3 days), and after treatment with the tachykinin antagonist SR-140333 (10-100 micrograms kg-1, i.v.) or the N-methyl-D-aspartate (NMDA) antagonist MK-801 (100 micrograms kg-1). 2. Peripheral effects mediated by afferent C-fibres were measured by plasma protein extravasation (Evans blue method), following antidromic stimulation of the sciatic nerve, topical application of mustard oil and, as control, i.v. injection of substance P. SR-140333 (100 micrograms kg-1) reduced the effects by 86%, 75% and 74%, respectively. Colchicine reduced the effects of the first two stimuli by 31% and 33% and, as expected not the effect of substance P. The increase of paw skin temperature following capsaicin i.v. was inhibited by SR-140333, but not by colchicine. MK-801 had no effect on the plasma protein extravasation following antidromic sciatic nerve stimulation or on the rise of paw skin temperature induced by capsaicin i.v., thus excluding an effect of MK-801 on peripheral terminals of afferent neurones. 3. Depressor reflexes, which are known to be mediated by capsaicin-sensitive afferent neuones, such as those elicited (A) by a stimulating dose of 30 ng capsaicin i.a., (B) by distension of the ascending colon or (C) by afferent sciatic nerve stimulation were studied. Colchicine significantly reduced depressor reflexes A and B, but had no effect on reflex C. None of the reflexes was affected by SR-140333. MK-801 significantly inhibited all three reflexes. 4. Capsaicin, injected either i.v. (200 micrograms kg-1) or into the nucleus caudatus/putamen (i.c., 30 micrograms), induced an increase in paw skin temperature and a decrease in colon temperature. The rise in fore paw skin temperature (delta t = 2.3 +/- 0.4 degrees C) evoked by capsaicin i.v. was almost completely blocked by SR-140333 (100 micrograms kg-1, i.v.), but no inhibition was observed with MK-801, indicating that capsaicin had brought about a release of substance P from peripheral nerve terminals. Colchicine did not influence heat dissipation induced by i.v. capsaicin. 5. When capsaicin was injected i.c., the rise in paw skin temperature in colchicine- and SR-140333-pretreated groups did not differ from that of the control group. MK-801 totally prevented the heat loss reaction to i.c. capsaicin administration. Colchicine did not change the effects of i.v. or i.c. injected capsaicin: this excludes the involvement of a mechanism dependent on axonal transport of neurotransmitters. 6. The reduction of axonal transport by colchicine reduced plasma extravasation induced by mustard oil and antidromic sciatic nerve stimulation (peripheral functions) and depressor reflexes evoked by i.a. capsaicin and colon distension (central functions). It can be argued that afferent stimulation of the sciatic nerve includes the stimulation of A-fibres, which might be less sensitive to colchicine. SR-140333 was effective only on peripherally mediated responses. 7. The recent evidence for the concomitant release of glutamate and substance P from central terminals of afferent C-fibres, known to mediate reflexes abolished after capsaicin treatment allows the following conclusions: (a) the inhibition by MK-801 indicates an essential role for glutamate in the central transmission of these reflexes; (b) tachykinin antagonists such as SR-140333 do not affect these responses when administered systemically. Centrally released substance P could be involved in functions of the CNS other than those investigated here unless the access of neurokinin antagonists to their receptors in the CNS is insufficient.

Lipid peroxidation during acute stress.

Lipid peroxidation (LPO) is one of the main events induced by oxidative stress. The aim of our study was to investigate the influence of 30 min cold-immobilization (model of acute stress used in this experiment) on LPO in the brain, heart, liver and stomach homogenates of the rats. LPO was determined by measuring of the contents of thiobarbituric acid reactive substances (TBARS), conjugated dienes (CD) and sulfhydryl groups (SH). Experimental stress induced enhancement of TBARS formation in the liver and increased level of the CD in the heart, stomach and liver, while in the brain both parameters were found to be decreased. The levels of TBARS were not changed in the heart and in the stomach, too. The concentrations of SH-groups were decreased in the heart, brain and stomach, while in the liver the parameter was found to be not changed. The results of this study showed the increase of LPO in the heart, stomach and liver under stress conditions. It could be supposed that LPO may be involved in mechanisms of stress injury in different tissues.

Effect of illuminated nifedipine, a potent antioxidant, on intestinal and vascular smooth muscles.

1. The effects of nifedipine (Nif) and its illuminated nitroso product nitrosopine (NTP) were investigated on lipid peroxidation, KCl elevated smooth muscle tension, and ionic currents of single smooth muscle cells. 2. Illumination of Nif at 400-700 nm within 24-48 h changed it completely to a potent antioxidant, NTP. 3. Nif relaxed the KCl-induced contractions of guinea-pig taenia caeci and rat aorta and reduced the amplitude of the evoked inward Ca2+ current of taenia caeci cells in a concentration-dependent manner. NTP (up to 100 microM) was ineffective in this respect. Pretreatment by NTP (10 microM) did not affect the actions of Nif. 4. The evidence suggests that NTP, generated by day-light illumination from Nif, exerts antioxidant activity but is devoid of voltage-dependent Ca2+ channel (VDC) blocking property and does not interfere with the action of Nif on the smooth muscle cell membrane VDC.

Effect of trapencaine and some of its derivatives on gastric wall mucus in stressed rats.

The effect of selected carbanilates on the rat gastric mucus was tested after oral administration. The compounds K 1905 and K 2002 were found to increase gastric mucus content in nonstressed rats while compound P 2 was ineffective. The activity of K 1905 was comparable with that of the parent drug trapencaine. Cold-restraint stress decreased the gastric mucus content and induced haemorrhagic erosions in the glandular stomach. With the exception of compound P 2 pretreatment with carbanilates dose-dependently diminished the extent of stress-induced gastric damage and prevented the depletion of mucus after stress. The results indicate that pentyloxy-substitution in the meta and in the para position on the benzene ring of the parent structure (K 1905 and K 2002, respectively) seems to be more suitable for mucus enhancing activity than alkyloxy-substitution on the para position (P 2). The observed increased mucus secretion might be partly responsible for the gastroprotective action of the drugs tested.

[Smooth muscle preparations as models for studies of drug effects on organs]. / Hladkosvalové preparáty ako modelové orgány stúdia úcinku farmák.

The action of drugs on processes in smooth muscles, in their innervation or mucosa results in changes in contractility of the gut, airways, vessels and urogenital system. Noteworthy insight has been gained into the basic common characteristics ot smooth muscles as well as into special properties of individual smooth muscle types whose fundamental properties have become adapted to a particular situation. This insight along with knowledge on the subcellular and cellular organization of smooth muscle cells and of their innervation, on the role of the mucosa, and introduction of sophisticated electrophysiological, biochemical, isotopic and morphological methods makes smooth muscle suitable for investigation of elemental physiological and pathophysiological processes and of targets of drug action. The complexity of the smooth muscle tissue allows to study the mechanisms of drug action on the peripheral cholinergic, adrenergic, nonadrenergic-noncholinergic nerves and their neuromediators, on the epithelial and endothelial cells and the biologically active substances which they release, on the membrane and subcellular receptors, receptor coupled processes, ion channels, enzymes, Ca2+ availability, etc. Since most of these mechanisms operate also in other tissues, the obtained results may characterize drug action in other systems as well.

Effect of oxidative stress on (3H)N-methylscopolamine binding and production of thiobarbituric acid reactive substances in rat cerebral cortex membranes.

We investigated the effect of lipid peroxidation, in vitro induced by H2O2 or FeSO4 and ascorbic acid, on binding properties of muscarinic receptors in rat cerebral cortex membranes. Simultaneously the concentrations of thiobarbituric acid reactive substances (TBARS) were measured to assess the extent of lipid peroxidation. In conditions of increased TBARS levels the density of (3H)N-methylscopolamine [(3H)NMS] binding sites in rat cerebral cortex membranes was not affected. Decreased numbers of (3H)NMS binding sites observed in the presence of high concentrations of H2O2 (100 and 1000 mmol.l-1) accompanied by a decrease of TBARS levels might be related to a nonspecific effect of H2O2 on cellular proteins.